Heat the oven to 375 degrees. Brush both sides of the mushrooms with olive oil and season with salt and pepper.

Place the seasoned mushrooms cap-side down on a baking sheet coated with Teflon® non-stick and bake for 10 minutes to soften. Let the mushrooms rest to drain while making the filling.

In a medium bowl, mix the onion, pears, chicken, thyme and half of the blue cheese. Turn the mushrooms over and replace on the baking sheet, draining off any juice. Fill the mushrooms equally with the stuffing.

Mix the remaining blue cheese and walnuts together with the apples and parsley and add to the top of the mushrooms. Return to the oven and place evenly over the top of each stuffed mushroom; bake another 20 minutes and serve.